Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import *
h, w = map(int, input().split())
s = [input() for _ in range(h)]
p = [[-1] * w for _ in range(h)]
p[0][0] = 1
d = ((1, 0), (-1, 0), (0, 1), (0, -1))
white = sum(row.count('.') for row in s)
queue = deque([(0, 0)])
clearable = False
while queue:
  x, y = queue.popleft()
  if x == w-1 and y == h-1:
    clearable = True
    break
  for dx, dy in d:
    nx, ny = x + dx, y + dy
    if not (0 <= nx < w and 0 <= ny < h):
      continue
    if s[ny][nx] == '#' or p[ny][nx] > 0 :
      continue
    p[ny][nx] = p[y][x] + 1
    queue.append((nx, ny) )
if clearable:
  print(white - p[h-1][w-1])
else:
  print(-1)